Study On The Technologic Parameter And Wear Model Of Retaining Ring In Chemical Mechanical Polishing Process

During CMP processes, over-grinding appears in the edge of wafer, which results in the decrease of planarization quality and the utilization of wafer. With the increase of the diameter of the wafer, over-grinding becomes more severity. The application of retaining ring can alleviate the over-grinding. In addition, the wear property of retaining ring has great influence on its natural life. At present, the technical parameters and the wear rate of the retaining ring are confirmed through trial or experience, which usually has longer periods, higher cost and larger waste. The paper mainly studies the technical parameters and the wear rate of retaining ring.The main work and the new outlooks are as follows:Two-dimensional axisymmetric static model for CMP system is established using Finite Element Method software ANSYS10.0. The Von Mises stress on the wafer can present the polishing quality because they are of direct proportion.The influencing disciplinarians of the technical parameters of retaining ring on the polishing quality are analysed. The P₂ (pressure on the retaining ring) /P-1 (the pressure on the wafer) and W (the gap between the wafer and retaining ring) have effectively influence. The influence of A (the width of retaining ring) can be ignored. In practice, after W is determined, P₂/P₁ exist an optimum value.FEM is very useful for the design and technique determination of retaining ring, which can overcome the waste resulting from the present trial method. The optimum value of P₂/P₁ is about 2. Then, P₂/P₁ and W can be optimized together with the judge of the most homogeneous pressure on the wafer.The pad asperities are assumed to follow the periodic and uniform distribution. The abrasive particles sizes are assumed to satisfy normal distribution. Then the relationship among the hardness of the pad and the retaining ring, the number of...